The Lotus Grand Tourers

Looking for a fuel sender for a 89 excel.

So I found this company with sells programmable dip style fuel gauges with programmable damping:

http://www.centroidproducts.com/pic-cal-4-1-2013.pdf
Can you super electronic geniuses confirm that this is workable with the VDO gauge? to include the Low Fuel light "alarm" output?

NEG: connect this to DC ground. NOTE: our senders only work with negative-ground systems.
SEND: connect this to the Send input of your gauge or display. NOTE: this is an electronic output which will confuse your
ohmmeter if you try to take a resistance reading. Instead we troubleshoot by voltages, while connected to the gauge.
POS (most senders): Most Centroid senders have an ignition-voltage POS terminal to run their electronics. A fused voltage
between 11-28vdc should be wired to the POS connection. The voltage should turn off when the system is turned off, both for
safety and to avoid running down the battery. For a number of brands of E240/F33 ohm gauge (not all), we can make a special
sender that doesn't have this POS connection. These senders run their electronics from voltage on the Send connection.
ALARM (if ordered): The ALARM output switches to ground. A DC load which requires 0.3A or less can be connected to this
output, with the far side of the load connected to ignition voltage.

5. CALIBRATION
The output range (eg E240/F33 ohms) and alarm levels (if ordered) are set at the factory per the customer's order. They cannot be changed by the end user. They can be changed for you back at the factory if needed, however.

From a different page on the website: D. FREE DAMPING
The programmable senders can be provided with averaged readings ("damping")


Thoughts? Is this the all-in-one solution I've been craving to replace my fuel sender?

Bumping this thread as I'm leaning toward putting a new fuel pump in to start the process of addressing my 1k-2k RPM hesitation. I figure if I'm going back to the pump, I might as well go back to the tank and replace the sender and get that working once a for all.... So what do you all think?? Will the item I listed above solve all the fuel gauge issues in one simple solution?

Side note: Anyone know the interior tank depth to where the tank is full? It's basically a cube shape correct? so I could just measure bottom to top in situ near as I can tell and take off 1/4" for thickness.

The Centroid product looks good. Things to check seem to be: Does the pattern of our VDO sender unit conform to the SAE bolt pattern used by the Centroid unit? It mentions on one of their web pages that some VDO gauges run "backwards" wrt the resistance pattern - is ours one of those?
I may have an old one in the shed I can look at. You're right about the tank - it is flat-bottomed and the top is parallel to the bottom.

Pete

Pete Boole wrote:The Centroid product looks good. Things to check seem to be: Does the pattern of our VDO sender unit conform to the SAE bolt pattern used by the Centroid unit? It mentions on one of their web pages that some VDO gauges run "backwards" wrt the resistance pattern - is ours one of those?
I may have an old one in the shed I can look at. You're right about the tank - it is flat-bottomed and the top is parallel to the bottom.

Pete

Yep the VDO runs backward. Something like 240 - 40 got exact figures at home somewhere from checking 1/4 empty and full resistance. So no longer need 2nd hand sender. So installation of Stack fuel gauge can go ahead

So, I want to order the fuel gauge I mentioned above and I took some measurements on my VDO fuel Gauge, check me to make sure I did this correctly, because the values I'm getting have me scratching my head...

METHOD:
I have a potentiometer wired to my fuel sender wires; they are parallel to the fuel sender's wires Black and Black w/green. However they are on the gauge side of the quick connect and the quick connect is disconnected so the (non-working) fuel sender is isolated from the circuit and the Pot essentially replaces the sender for sending signal to the gauge. The Green w/ orange wire is not in the mix - this is the low fuel light signal as far as I'm aware.

The potentiometer is a 300 Ohm 5 Watt linear unit and moving through 60-70% of its range moves the needle from Full to Empty which tells me it's a 240-33 Ohm Gauge (Nearly Maxed out (if it was a stereo volume knob, "10" gives me an Empty reading, turning the volume 'down' makes the gauge read more full). It reads full around "4" and pegs the needle at full the rest of its travel to "0"; However, The meter readings tell a different story:

TESTING: I energize the car and turn the potentiometer until the gauge gives a reading I'm seeking to get an ohm reading for. (Empty, Full, Half tank etc.) I then turn off the ignition and take a reading with a trusted meter with new battery. This is taken by contacting the leads of the BLK and BLK w/GRN wires at the quick connect plug. Here's the rub, my numbers aren't quite what I expected as they don't agree with any 'normal' range of fuel senders, they're close to a reversed 180-10, but not the expected 240-33, in fact it seems to be exactly half that!!!

RESULTS:
Needle Reading - Ohm reading
Overfull but not pegged - 136 Ohm
4/4 - 128
3/4 - 118
2/4 - 96
1/4 - 69
0/4 - 19
Below Empty but not pegged - 13 Ohm

Am I missing something in my testing method?

What's the impedance of the gauge?

So, I had a minor revelation after thinking your question over a bit...

What I failed to do in my method was separate the POT from the circuit before taking the measurement, so I think What Angus was asking about is in effect why my readings are odd, I'm measuring incorrectly. I'm going to do it again tomorrow by setting the Gauge needle, then disconnecting the POT and seeing where it sits isolated from the system. I'm pretty confident I'll find the standard measures I expect of the VDO.

I wish I was Smarter at electronics. I know enough to have the confidence I think I know what I'm doing, but often don't.
Thanks for pointing me in the right direction (I hope)

Results confirmed. 240-33 Ohm. (13 ohms still registered below E.)
Think I'm going to pull the trigger on the sender I noted above. My tank does appear to have the ANSI 5 hole mount as someone had questioned.

Bill, I think that sender will run your gauge backwards. I'm reading E240/F33 as empty 240, full 33.

Most adjustable simple senders can have the float arm reversed to switch the full setting from high resistance to low, but I doubt a microprocessor one will have that as an easy option.

They can program it to be E33-F240 (i wrote those numbers backwards above). I just want to make sure it's right the first time.

So Angus, your saying yours is 'normal 240-33?? I can't convince myself mine is like that. Is there any experience with Lotus putting in non-standard 'inverted' resistance ranged gauges? God, this whole thing is racking my brain.
I guess the worst case is my fuel goes from Empty to Full while I drive!!!

TBH, I don't know what Lotus did, but when I changed the tank on the Westfield and fitted a new sender, I know I had to reverse the float arm to reverse the resistance range.

So, After extensive testing ICW the centroid companies Tech, we have come to the conclusion that my gauge is unusual!!!
I suspect, we are going to program the sender with the following Ohm ratings:

Empty 10
1/8 25
1/4 55
3/8 70
1/2 90
5/8 120
3/4 165
7/8 175
Full 220

The VDO gauge could handle 240, but it would read 'over full'.
For Empty, a 33 obviously wouldn't produce an Empty looking condition.
FWIW, my gauge was stamped in the plastic housing with markings as follows:
301.292/4/5 12v VDO
A082N60.11F 02.90.
301.292 matches VDO model number structuring, these six digits apply moreso to marine gauges though. Here:
https://www.vdo-instruments.com/instrum ... 2-24v.html
Further, I can't determine what the /4/5 represents, I've seen other gauges with /xxx/xxx following the first 6 digits like in the link above, perhaps /4/5 was a shortcut for /004/005??
The 02.90 is likely the manufacture date and I have no clue about the A082N60.11F perhaps a lot number?
Anyway, Hopefully I'll have it ordered Monday and can get it in next weekend.
I'll keep this thread updated as it goes. Good or bad.

A082 looks like an Esprit part number. Maybe one grabbed from the parts bin?

Glad you seem to be getting to the bottom of this Bill . Keep us posted on the results of your new sender unit - it looks good.

Pete